The present invention relates generally to cartridges containing a continuous loop of ribbon, especially fabric ribbon, for use in printers associated with equipment such as computers and word processors. More particularly, the present invention relates to a method and apparatus for loading an assembled cartridge with a predetermined length of ribbon from a ribbon spool. Still more particularly, the present invention provides an improved method and apparatus for loading ribbon into a preassembled printer cartridge whereby the speed and reliability of the loading process is greatly enhanced.
Present society is highly dependent on the use of microprocessors, minicomputers, and mainframe computers. In addition to the more traditional use of computers as a research tool, computers are now often found in the home environment and work environment of individuals who, until recently, never before came into contact with a computer. Computers are used to automate equipment in a manufacturing facility, to automate secretarial duties at the office (word processors), and to automate a myriad of toys and tools around the home.
All computers, whether mainframe computers, minicomputers, or microcomputers, share a common requirement for some means of communication with users. Such means of communication may vary from a simple light-emitting diode (LED) to the complex cathode ray tube (CRT) terminal. A common means for communication of information from a computer to a user is a printer. Printers typically receive from a computer a stream of information in the form of digital electronic signals and convert the electronic signals to a series of symbols (letters and words) printed on paper.
A first common type of printer is an impact printer, so named for the means by which characters are printed on paper. Each symbol which the impact printer is capable of generating is permanently embossed on a striking surface (analogous to the ball within a typewriter) within the printer. The printing of a particular character is accomplished by aligning the embossed image of that character with the paper surface onto which the character is to be printed, positioning a printer ribbon having ink thereon between the striker and the paper, and causing the striker to impact the ribbon against the paper surface so as to result in an ink image of the embossed character on the surface of the paper. Printer ribbons typically are made of fabric, such as nylon, or polyester film coated with a carbon-type surface.
A second common type of printer is a dot matrix printer. Such a printer includes a group of small-diameter wires oriented parallel to one another and arranged in a two-dimensional matrix. Each wire is arranged for independent extension from its normal matrix position to contact a printer ribbon, thereby printing a dot image on an adjacent paper surface. By selectively extending particular patterns of wires, dot images can be combined to form alphanumeric or other legible characters on the paper surface.
In approximately 1970 there first appeared on the market a printer ribbon having the ends thereof adjoined to form a continuous loop. The continuous loop ribbons are housed within cartridges which easily may be removed from and inserted within the printers. Such continuous loop cartridges mechanically simplify the ribbon control portion of printers and thereby eliminate a potential source of printer failure.
A number of companies throughout the world today are engaged in the business of manufacturing and/or loading printer ribbon cartridges. Typically, ribbon is manufactured, inked, and spooled into large, narrow rolls. For some time, ribbon cartridges have been manufactured and delivered unassembled to the point of cartridge loading, so that the inked ribbon from the ribbon spool could be threaded through the operative parts of the cartridge before assembly thereof.
U.S. Pat. No. 4,050,617 (Biggs et al.) depicts an apparatus for loading ribbon into unassembled cartridges. The apparatus of Biggs threads the end of the inked ribbon between a cartridge capstan and a cartridge drive gear and through the cartridge before clamping the lid onto the cartridge base. Thereafter, the apparatus rotates the drive gear within the cartridge to draw ribbon into the cartridge. As ribbon is pulled into the cartridge, rotation of the drive gear is monitored to measure the length of the ribbon being loaded into the cartridge. A microswitch pressing the ribbon against a roller detects splices in the ribbon when the thickness of the ribbon exceeds 0.005 inch. Finally, a cutoff blade severs the ribbon when the cartridge is loaded and grasps the end of the ribbon from ribbon roll for threading through the next cartridge.
The apparatus of Biggs would appear to function reasonably well for loading the particular type of cartridge for which it was designed. The use of a cammed front plate and a cam follower apparatus for threading the ribbon through the cartridge, however, restricts the application of Biggs' apparatus to the single cartridge for which it was designed. Thus, each of the more than sixty different cartridge configurations could require the design and construction of a separate loading apparatus--obviously a very expensive proposition for one in the business of manufacturing and loading printer ribbon cartridges.
Part of the problem is resolved by eliminating from the cartridge loading apparatus portions thereof used exclusively for threading operations. Recently, many manufacturers have begun the practice of assembling the cartridge at the point of manufacture and including on assembly a short "leader" ribbon extending through the cartridge. Thereafter, at the point of cartridge loading, the inked ribbon is taped to the leader ribbon by an operator and pulled through the cartridge. See U.S. Pat. No. 4,415,285. A cartridge loading apparatus then is used to stuff the cartridge with the inked ribbon.
In a process known generally as "restuffing," a ribbon cartridge is recycled by removing the spent printer ribbon and restuffing the cartridge with newly inked ribbon. A leader ribbon may be formed in a used cartridge by leaving a short length of the old ribbon running through the cartridge.
Applicant is aware of several companies engaged in the manufacture of apparatus for loading printer ribbon into cartridges, including Computer Ribbon Machinery GmbH of Berlin, West Germany, and MSS Supply Corporation of Halesite, N.Y. Although Applicant is not aware of the particular details of the cartridge loading apparatus manufactured by such companies, it appears that such apparatus, like the apparatus of Biggs, will function adequately to load the ribbon into cartridge, but includes certain structural inefficiencies which have an impact on the overall cost of the cartridge loading process. For example, the adaptability of any one cartridge loading apparatus to various cartridge configurations depends on the purchase of various fixtures. Typically, such fixtures are sold separate from the apparatus itself. In at least one case, a complete set of fixtures for the apparatus is more expensive than the apparatus itself.
Another example of inefficiency lies in the cost of labor required to operate the apparatus. Quite obviously, time is money. Yet, the myriad of cartridge configurations seems to have stymied the development of an efficient loading apparatus. Manufacturers seem to have gotten little beyond the use of a motor to pull ribbon into the cartridge. The inherent limitations on the cartridge loading process understandably have had their toll. Cartridge loading speed is limited by the cartridge and by the ribbon. Cartridges are assembled from molded plastic parts which are manufactured as inexpensively as possible. Consequently, there is a definite limit to the amount of stress which the cartridge, particularly the drive gear and drive capstan, can withdstand without suffering damage. In addition, care must be exercised to limit stress on the inked ribbon as it is pulled by the cartridge drive gear off of the ribbon roll and through the cartridge. Certain manual operations, such as placing the cartridge onto the apparatus or taping the inked ribbon to the leader ribbon, or, in some cases, cutting the ribbon after loading expend significant amounts of operator time. Changing rollers and other parts of the prior art apparatus in order to accommodate different ribbon widths consumes inordinate amounts of time.
Hence, although there presently exists apparatus for loading printer ribbon into cartridges, it should be apparent that such apparatus may be improved in structure and operation to enhance its speed and reliability and therefore to improve the cost effectiveness of the cartridge loading process.